An increased flow resistance in the various coronary vessels can jeopardise the oxygen supply to the cardiac muscle. In some cases an expansion of vascular stenosis is possible. If the flow of blood in a vessel is completely or practically completely blocked, the only thing to be done is to bypass the blocked portion to prevent an irreparable injury from arising. Such a bypass operation is usually effected by connecting a new vessel after the blocked point and connecting it to another blood vessel, for instance the aorta, which may give a sufficient flow of blood to the blood vessel after the blocked point.
In practice, such a bypass operation requires the use of a heart-lung machine, i.e. that the heart be temporarily stopped since the bypass operation when connecting, for instance, the two vessels involved requires the heart to be immovable. In consequence of the connecting technique employed and the use of the heart-lung machine, the operation will be relatively time-consuming and not completely without risk.
When larger vessels are involved, it is known from e.g. U.S. Pat. No. 5,456,712 to provide a branch by blocking the vessel by means of balloons on each side of the intended branch point, whereupon an incision is made in the blocked portion of the blood vessel. Then an expanded end of a vascular prosthesis is inserted through the incision and a stent is inserted through the one blocking balloon to a position inside the incision, where finally the stent is expanded by means of a further balloon positioned inside the stent. For completely safe fixing of the expanded end to the area around the incision in the vessel, some sort of suture is used, primarily for connecting the expanded end of the vascular prosthesis with the blood vessel around the incision therein.
The prior-art technique implies that a blocking can be made on each side of the intended branch point, and that the stent can be inserted via the diseased vessel involved and through one of the blocking balloons. In practice, also a fixing of the expanded end of the vascular prosthesis relative to the vessel involved by means of some sort of suture is required.
The technique according to U.S. Pat. No. 5,456,712 is thus not suited for use in thin vessels, such as the coronary vessels, or in other positions where the described blocking by means of a balloon from the inside of the vessel is not possible.